To a hydraulic actuator constructing a speed change clutch provided in a vehicular automatic transmission and driven by an oil pressure, a suitable oil pressure regulated by a hydraulic control device is supplied. The oil pressure pumped up by, for example, a mechanically-operated oil pump is supplied to the hydraulic actuator as an initial pressure.
A hydraulic control device for vehicular hydraulic control circuit has been known which includes a mechanically-operated oil pump and an electrically-operated oil pump to suitably drive these oil pumps in accordance with the running state of the vehicle. For example, a hydraulic control device disclosed in Patent Literature 1 (Japanese Patent Publication No. 2003-307271A) is one example thereof. The vehicular hydraulic control circuit disclosed in Patent Literature 1 includes an electrically-operated oil pump and a mechanically-operated oil pump which are connected to an internal combustion engine to be driven by it in an interlocking manner.
For example, since the mechanically-operated oil pump is held in a non-driven state during non-operation of the internal combustion engine, the electrically-operated oil pump is driven to supply an oil pressure. Additionally, Patent Literature 1 discloses a technique for increasing a target rotation speed of an oil pump motor that drives the electrically-operated oil pump in accordance with the running state of the vehicle, thus quickly starting up the oil pressure.
By the way, in the hydraulic control device for vehicular hydraulic control circuit disclosed in the Patent Literature 1 and the like, when the electrically-operated oil pump is rapidly rotated during non-operation of the internal combustion engine, a load imposed on the electrically-operated oil pump may momentarily increase. This is caused by, for example, the operating resistance of a valve, such as a pressure regulating valve, disposed downstream the electrically-operated oil pump. Especially, when the operation oil is low in temperature due to large viscosity thereof, a load imposed on the electrically-operated oil pump may greatly increase. As a result, there has been a fear that excessive current will be generated in an electronic control circuit that controls electric power supplied to the electrically-operated oil pump.